Codes for uniform dating
On this site, all ZIP code maps use the ZIP Code Tabulation Areas (ZCTAs) as specified by the United States Census Bureau in 2010 (or newer) and discussed below.They provide a very close approximation of the area covered by a ZIP code.You can easily notice some of the boundary issues when viewing our maps.
Some ZIP codes will span multiple states in order to make mail routing and delivery more efficient.
The additional 4 digits help USPS more precisely group mail for delivery.
The basic 5-digit format was first introduced in 1963 and later extended to add an additional 4 digits after a dash to form a ZIP 4 code.
In areas without a regular postal route or no mail delivery, ZIP codes may not be defined or have unclear boundaries.
No official ZIP code map according to actual USPS data exists.